Gull populations on a Scottish island have suffered as a result of a declining quantity of fish landed

Research published in the British Trust for Ornithology (BTO) journal Bird Study, looked at the breeding populations of Herring Gull, Great Black-backed Gull and Lesser Black-backed Gull on the Hebridean island of Canna, and the relationship between them and the fall in the quantity of fish landed in the nearby harbour of Mallaig.

Between 1985-2000, an annual average of 13,726 tonnes of fish was landed there, but between 2007-2014, this fell to 4,456 tonnes. The number of breeding pairs of Herring Gulls peaked at 1,525 in 1988, Great Black-backed Gulls reached 90 pairs around the same time and the highest number of Lesser Black-backed Gulls was 63 pairs.

But at the last count, breeding gulls on Canna were 95 pairs of Herring Gulls, 18 pairs of Great Black-backed Gulls and 13 pairs of Lesser Black-backed Gulls. This population decline has also been associated with low breeding success, with only a small number of chicks successfully fledging in more recent years.

Dr Viola Ross Smith, gull expert at the BTO, said: “Breeding gulls have a bad reputation, especially in urban areas, but it is worth remembering that all these species are classed as Birds of Conservation Concern, and the Herring Gull is on the Red List. It therefore seems important to identify the causes of population decline in rural colonies such as Canna, and find ways to conserve the birds at these sites, especially since gulls that fail to breed successfully are known to seek breeding opportunities elsewhere, including in towns and cities.”